InfoDroid said:
The way I understand it is, the Sith are kind of like a secret society. They officially "don't exist". No one knows the Emperor or Darth Vader are Dark Lords of the Sith by the time we get to ANH. And any suggestion of that is probably passed off as ridculous, politically-motivated rumor. It's not public knowledge, and probably not something they want to advertise given the Sith's long dubious history.

Like David Icke's shape shifting lizards of the Illuminati, I suppose (that would explain the eyes)?